Odd-electron sigma bonding in medium-ring bicyclic bridgehead radicals.

摘要

y research has combined multi-step organic synthesis with physical and computational studies to explore medium-ring bridgehead radicals. The results of MNDO and ab initio HF/6-31G;My synthetic work centered on developing routes and efficient precursors to atrane-like bicyclics, whose corresponding bridgehead organic radicals could provide a potentially long series of compounds for the investigation of intrabridgehead through-space ;Chapters 5 and 6 describe additional computational work. Inspired by the hybridization change of the bridgehead carbons in manxane and manxine, associated with decreased one-bond C-H couplings, we explored the prediction, from standard quantum chemical models, of C-H couplings in a series of bi- and polycyclics. Lastly, the availability of the RHF/6-31G;The research described herein was motivated by the challenge of designing species that can be used to probe theories of structure and bonding. The unusual properties of the bicyclo (3.3.3) system are a consequence of the geometry and strain inherent in a bicyclic array made up entirely of eight-membered rings. Our foray in the field of medium-ring bicyclic radicals revealed unforeseen opportunities for further work in this area.;Description of the synthesis, kinetics, spin trapping, EPR, ENDOR and computational studies, of bicyclo (3.3.3) undec-1-yl (1-manxyl) radical, a key reference species for medium-ring bridgehead radicals, now generated in solution from manxane by H-abstraction with tert-butoxyl radicals, is given in Chapter 2. The exceptional persistence of this sterically open radical is unique and is attributed to the high strain of all its decomposition products. (3.3.3) Propellane has been identified among the decay products of 1-manxyl radical; its formation was rationalized by a novel